I am looking for a way to move the timeline a specific amount, scroll, etc. even if the Timeline window is not open. Is this possible?
Hold down the Alt button and start scrolling the Mouse Wheel.
Scrolling down will let you go forward in a Timeline, scrolling up works vice versa. You can do it in almost every window type you want and it works even if the Timeline window is not open.
(I know this is an old question, but I got here while looking for an answer. So, just for the record...)
You can change the size of "steps" (or "jumps") Blender does (when pressing Left/Right, Shift + Up/Down, and even Alt + Wheel/Scroll) by changing the "Delta" parameter in the shortcuts "Frame Offset".
Path: Blender User Preferences > Input > search for a shortcut named "Frame Offset". Then change the "Delta" value to whatever you want (default is 10).
Here are some examples... (customize to your liking)
Location: Preferences → Keymap → Frames
Jump 10 frames forward / backward
ShiftAltWheel Down / ShiftAltWheel Up
Jump to next / previous keyframe
CtrlAltWheel Down / CtrlAltWheel Up
Jump to end / start of playback range
ShiftCtrlAltWheel Down / ShiftCtrlAltWheel Up
Note: I could not find commands in the Keymap Preferences for Next / Previous Marker. I'm not sure if they still exist in 2.8+
Hopefully some will find this useful, as you can leave your hand on the modifier keys instead of having to move it over to the arrow keys each time you want to move along the timeline. A configuration like this seems to allow the shortest keyboard travel time.
Note: When configuring shortcuts, checkboxes for "Next Keyframe" or "Last Frame" etc. are greyed out by default. You must click to interact with them to make them active, otherwise these shortcuts won't register. In other words, greyed out does not mean FALSE.